A categorification of the square root of -1
We give a graphical calculus for a monoidal DG category ℐ whose Grothendieck group is isomorphic to the ring ℤ[√(-1)]. We construct a categorical action of ℐ which lifts the action of ℤ[√(-1)] on ℤ².
A characterization of discrete linearly compact rings by means of a duality
A characterization of representation-finite algebras
Let A be a finite-dimensional, basic, connected algebra over an algebraically closed field. Denote by Γ(A) the Auslander-Reiten quiver of A. We show that A is representation-finite if and only if Γ(A) has at most finitely many vertices lying on oriented cycles and finitely many orbits with respect to the action of the Auslander-Reiten translation.
A characterization of representation-finite biserial algebras over a perfect field [Book]
A class of quantum doubles of pointed Hopf algebras of rank one
We construct a class of quantum doubles of pointed Hopf algebras of rank one . We describe the algebra structures of by generators with relations. Moreover, we give the comultiplication , counit and the antipode , respectively.
A class of quasitilted rings that are not tilted
Based on the work of D. Happel, I. Reiten and S. Smalø on quasitilted artin algebras, the first two authors recently introduced the notion of quasitilted rings. Various authors have presented examples of quasitilted artin algebras that are not tilted. Here we present a class of right quasitilted rings that not right tilted, and we show that they satisfy a condition that would force a quasitilted artin algebra to be tilted.
A classification of symmetric algebras of strictly canonical type
In continuation of our article in Colloq. Math. 116.1, we give a complete description of the symmetric algebras of strictly canonical type by quivers and relations, using Brauer quivers.
A classification of two-peak sincere posets of finite prinjective type and their sincere prinjective representations
Assume that K is an arbitrary field. Let (I, ⪯) be a two-peak poset of finite prinjective type and let KI be the incidence algebra of I. We study sincere posets I and sincere prinjective modules over KI. The complete set of all sincere two-peak posets of finite prinjective type is given in Theorem 3.1. Moreover, for each such poset I, a complete set of representatives of isomorphism classes of sincere indecomposable prinjective modules over KI is presented in Tables 8.1.
A cluster expansion formula ( case).
A computation of positive one-peak posets that are Tits-sincere
A complete list of positive Tits-sincere one-peak posets is provided by applying combinatorial algorithms and computer calculations using Maple and Python. The problem whether any square integer matrix is ℤ-congruent to its transpose is also discussed. An affirmative answer is given for the incidence matrices and the Tits matrices of positive one-peak posets I.
A construction for quasi-hereditary algebras
A construction of complex syzygy periodic modules over symmetric algebras
We construct arbitrarily complicated indecomposable finite-dimensional modules with periodic syzygies over symmetric algebras.
A Continuity Criterion for Functors.
A Criterion for Finite Representation Type.
A criterion for quasi-heredity and the characteristic module.
A density theorem for algebra representations on the space (s)
We show that an arbitrary irreducible representation T of a real or complex algebra on the F-space (s), or, more generally, on an arbitrary infinite (topological) product of the field of scalars, is totally irreducible, provided its commutant is trivial. This provides an affirmative solution to a problem of Fell and Doran for representations on these spaces.
A density theorem for F-spaces
A duality result for almost split sequences
Over an artinian hereditary ring R, we discuss how the existence of almost split sequences starting at the indecomposable non-injective preprojective right R-modules is related to the existence of almost split sequences ending at the indecomposable non-projective preinjective left R-modules. This answers a question raised by Simson in [27] in connection with pure semisimple rings.
A family of noetherian rings with their finite length modules under control
We investigate the category of finite length modules over the ring , where is a V-ring, i.e. a ring for which every simple module is injective, a subfield of its centre and an elementary -algebra. Each simple module gives rise to a quasiprogenerator . By a result of K. Fuller, induces a category equivalence from which we deduce that . As a consequence we can (1) construct for each elementary -algebra over a finite field a nonartinian noetherian ring such that , (2) find twisted...
A functor between categories of regular modules for wild hereditary algebras.